1. Field of the Invention
The present invention relates to a method for transferring a graphene layer, and more specifically to a method for transferring the graphene layer by an electrostatic adsorption technique.
2. Description of the Prior Art
Transparent conductive materials have a very important role in display and solar energy industries. Most of the common transparent conductive materials are n-type metal oxides, which provide high conductivity through providing oxygen vacancies in a structure thereof and doping of other ions or chemical compounds. Among others, indium tin oxide (ITO), due to its superior conductivity, has become an irreplaceable choice in a current panel industry. However, since there is only a limited indium resource, a cost of an ITO target is constantly increased in recent years. Further, when an ITO film is bent, the conductivity thereof is reduced, rendering ITO not suitable for flexible elements. Therefore, there is an imminent need for finding an alternative to ITO.
A discovery of one-atom-layer and suspended graphene in 2004 by A. K. Geim and his researcher team at Manchester University (UK) started a series of researches on graphene. Then, physicists of M. S. Fuhrer's team at Maryland University (USA) proved that graphene at room temperature has an electron mobility higher than that of any other known materials. They also proved that thermal vibration has only very small hindrance to a migration of electrons in graphene. In graphene, vibrating atoms at room temperature generate a resistivity of about 1.0 μΩ-cm, which is less than 35% of the resistivity of copper, and making graphene the lowest-resistivity material known at room temperature. The low resistivity and an ultra-thin nature of graphene also allow an application of graphene in thin and tough transparent conductive films. A single-layer graphene layer absorbs only about 2.3% of visible lights.
At present, as a method for transferring a large-area graphene layer, there is a preferable solution in which a high-quality graphene layer is produced on a metal substrate via chemical vapor deposition (CVD), then the high-quality graphene layer is transferred on a substrate as required by a roll-to-roll process (refer to: X. Li et al., Large-area synthesis of high-quality and uniform graphene films on copper foils, Science, 324, 1312-1314, 2009 and S. Bae et al., Roll-to-roll production of 30-inch graphene films for transparent electrodes, Nature Nanotechnol., 5, 574-578, 2010). The above solution shows the most promise in lower costs and scalability for transferring the large-area graphene layer.
However, the metal substrate is supported by a thermal release tape in the solution, and then the high-quality graphene layer is transferred on the substrate as required. Therefore, a problem of retaining organic residues is generated in the manufacturing process, so as to worsen an electrical property of the graphene layer.
Therefore, there is a need to provide a method for transferring a graphene layer that can solve the problem of retaining the organic residues.